1. Field of the Invention
The present invention relates to a contactless cardiopulmonary signal estimation method and apparatus, and more particularly, to digital signal processing for more simply and accurately estimating a cardiopulmonary signal based on a characteristic of each of a heartbeat signal and a respiratory signal of a user.
2. Description of the Related Art
Recently, various methods are being proposed to monitor biosignals in an information technology (IT)-medicine convergence field including IT medical devices, ubiquitous health (u-health), and home care. In particular, various methods for measuring and monitoring cardiopulmonary signals in a contact manner or a contactless manner have been proposed.
To measure a cardiopulmonary signal, a continuous wave (CW) radar may be used. The CW radar may measure a Doppler shift amount of a reflection signal during periodical movement x(t) by a cardiopulmonary exercise in a state in which an object does not move, that is, there is no net velocity. To overcome a null point of a single receiver, a quadrature receiver with a phase difference of 90° may be used.
In an existing filter-based cardiopulmonary signal estimation scheme, a reception signal of a CW radar may be transformed to a digital signal, a heartbeat signal and a respiratory signal may be separated using a filter, and a cardiopulmonary signal may be estimated. However, because the filter is used to separate the heartbeat signal from the respiratory signal in the existing filter-based cardiopulmonary signal estimation scheme, operation complexity may be increased and an estimation error may occur.
Accordingly, a method of estimating a cardiopulmonary signal without using a filter to overcome the above disadvantage has been proposed. However, due to smearing and leakage, it may be difficult to detect signal components adjacent to a strong signal.
Additionally, a cardiopulmonary signal estimation method based on a RELAX algorithm to minimize the smearing and leakage has been proposed.